GB743747A - Improvements in or relating to hydraulic speed governors - Google Patents

Abstract

743,747. Fluid-pressure servomotor control systems. MASSEY MACHINE CO. July 29, 1953, No. 21043/53. Class 135. A hydraulic speed governor for an engine, in which the throttle response for small speed changes is slow and for large speed changes rapid, comprises an engine driven sleeve 15, housed in a casing 14 and slidably mounting a valve piston 16 responsive to flyweights 20 carried on arms 21 pivoted to the sleeve at 22 and the valve at 24 so that increase in engine speed moves the valve downwards. Pressure liquid supplied by an engine-driven pump 25 is directed by the valve to one or other side of a double-acting piston 44 operatively connected to the engine throttle and returned therefrom to a tank 53. Pistons 61, 66 connected to the valve piston 16 and the piston 44 respectively, on increase in engine speed, move to decrease the volumes of chambers 62, 68 interconnected by a line 71 and, on decrease in engine speed, move to increase the volumes of these chambers. A line 73 connecting the chamber 68 to the tank has an adjustable throttle 75 and a cylinder 80 housing a piston 82 loaded on either side by centralizing springs 88, 89 and having an orifice in its head controlled by a non-return check valve 100. On a small increase or decrease in engine speed the rate at which the piston 44 moves and hence the engine throttle responds is dependent upon the rate at which liquid can leave or enter the line 73 past the throttle 75. The desired response being obtained by the setting of the throttle 75. In the event of a large increase in engine speed consequent upon a sudden decrease in load, the piston 82 moves rapidly upwards to increase the volume below it and so offset the decrease in volume of the chambers 62, 68 and permit rapid movement of the piston 44 and a rapid throttle response. This is followed by a momentary opening of the check valve 100 and the subsequent return of the piston 82 to its neutral position. In a modification, the piston 82 and the check valve 100 are housed in separate chambers. In another arrangement, the check valve is arranged to open in the opposite direction so that on a large decrease in engine speed consequent upon a sudden increase in load the throttle will be rapidly moved to restore the engine speed to its set value. Specification 666,991 is referred to.